A solid polymer-type fuel cell may be miniaturized to reduce weight because of generation of high power density and low temperature operability and is expected to be put in practical use as a power source for automobiles, a power source for stationary electric power generation, power generation equipment for mobile devices and the like.
A solid polymer-type fuel cell is provided with a pair of electrodes disposed on both sides of a proton conductive solid polymer electrolyte membrane, and generates electric power by supplying pure hydrogen or reformed hydrogen as a fuel gas to one electrode (fuel electrode) and an oxygen gas or air as an oxidant to the other electrode (air electrode).
An electrode for such a fuel cell is composed of an electrode electrolyte on which a catalyst component is dispersed (hence this electrode may be called an electrode catalyst layer in some cases), and the electrode catalyst layer on the fuel electrode side generates protons and electrons from the fuel gas, while the electrode catalyst layer on the air electrode side generates water from oxygen, protons and electrons, enabling the solid polymer electrolyte membrane to ionically conduct protons. Thus, electric power is generated from such electrode catalyst layers.
A conventional solid polymer-type fuel cell has used a perfluoroalkylsulfonic acid-type polymer represented by Nafion (trademark) as an electrode electrolyte. Although this material is excellent in proton conductivity, it is very expensive and its low combustibility resulting from many fluorine atoms within its molecule makes it very difficult to recover and recycle expensive noble metals such as platinum used as an electrode catalyst.
On the other hand, various non-perfluoroalkylsulfonic acid-type polymers have been investigated as alternative materials. In aim to use those at a high temperature condition where the efficiency of power generation is high, high heat-resistant aromatic sulfonic acid-type polymers is attempted to use as an electrode electrolyte, particularly with a view to an application under
For example, Japanese Patent Laid-Open Publication No. 2005-50726 (Patent Document 1) has disclosed the use of sulfonated polyarylene polymers as an electrode electrolyte and furthermore, Japanese Patent Laid-Open Publication No. 2004-253267 (Patent Document 2) has disclosed the use of particular sulfonated polyarylenes.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2005-50726    Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-253267